The present invention relates generally to silicate compositions, and more particularly, to acrylic and methacrylic silicate materials and copolymers thereof with optically transparent polymerizable materials to form corneal contact lenses. In another aspect, the invention relates to the method of making and using acrylic silicates and to certain co-polymerizable acryloxy alkoxy silicates also useful in such applications.
In recent years, after the general concept of corneal contact lenses became accepted, it became apparent that such contact lenses required improvement in certain areas. Specifically, while some corneal contact lenses afforded great comfort because they were made from soft or relatively flexible materials, such as hydoxyethylmethacrylate ("HEMA") and derivative materials able to absorb water of hydration, or from elastomeric silicone materials, these lenses had their own inherent drawbacks, including but not limited to lack of durability, imprecise optical characteristics, and in some cases difficult processability.
Recently, a number of compositions have been suggested and/or made which are useful in making hard or semi-hard contact lenses, which in turn offered some of the optical advantage of hard lenses, and which also offer greater gas permeability as a way of providing extended and more comfortable wear for the user. As with other commercial products, however, these products are capable of further improvement in one or more areas.
It is known that the cornea of the human eye requires a constant supply of oxygen. Consequently, hard contact lenses of increased gas permeability provide the potential for extended wear, and in some cases, improved user comfort in relation to prior hard lenses. An ideal contact lens permits the cornea of the eye to be comfortably bathed in lachrymal fluid, and to receive a continuing, fresh supply of atmospheric oxygen.
Such a lens should have a proper fit on the cornea so that it will remain in place without discomfort, preferably being able to be oriented so that it can provide proper astigmatic correction and, in many cases, offer the potential for a bifocal lens which may be precisely located on the eye and which will remain there in use.
An ideal lens is also one which will resist bacterial contamination and which may be cleaned from time to time by simple methods; in other words, one wherein elaborate procedures for sterilization are not required. Certain HEMA lenses suffered from the drawbacks of actual or potential ease of contamination and difficulty of cleansing.
Still further, an ideal lens is one which copes well with other conditions encountered in use, including resistance to collection of mucus, and retention of dimensional stability and optical characteristics in use on the eye. The patent literature contain numerous reference to acrylic silanes per se, as well as reference to the combination of known polymerizable acrylic silane monomers with themselves or similar compounds, and with conventional polymerizable acrylate materials such as methyl acrylate, ethyl acrylate, and methyl methacrylate ("MMA"), for example. It is known to use conventional wetting agents such as N-vinyl pyrrolidone, methacrylic acid and the like, in conjunction with these materials and with cross-linking agent adapted to impart greater rigidity and other desirable characteristics to the finished product. These include ethyleneglycoldimethacrylate, triethyleneglycoldimethacrylate and other polyfunctional acrylates.
Typical patents referring to the general subject of these compositions include U.S. Pat. No. 3,377,371 (Quaal); U.S. Pat. No. 3,808,178 (Gaylord); and U.S. Pat. No. 4,216,303 (Novicky).
All of the foregoing patents describe compositions having certain gas permeability and other desirable characteristics. However, corneal contact lenses of the type referred to above are, and have been, capable of further improvement, including improvement in one or more desirable characteristics, and the ability to be manufactured from existing materials by known, repeatable methods.
The ability to make contact lenses having a relatively high permeability, and in particular, compatibility with other gas permeable polymers so that a fused type of bifocal lens can be made therefrom, are also desirable characteristics of improved contact lenses. In this connection, inasmuch as a fused bifocal contact lens normally includes a bifocal segment made from a different material than the distant vision segment, and by reason of having different front curvatures on two segments, it is inherently thicker than a normal single vision lens of the same power, and hence, less tolerant in use of materials having a low index of gas permeability.
According to the present invention, improved polymerizable silicates and polymers made from these silicates are able to be made which provide good chemical and physical characteristics, good optical characteristics, and other advantages, including high oxygen permeability in use.
It has been known that silicate materials have desirable characteristics, but certain prior art silicates have had drawbacks and disadvantages which have heretofore believed to prevent their effective use in applications such as copolymers in gas permeable contact lenses. According to the invention, compositions are provided which may be copolymerized with other acrylic materials, including other acrylic silicates, and organic acrylates of conventional types to make stable, gas permeable products.
In view of the failure of the prior art to provide reactive acrylic silicates and materials made therefrom which are suitable for use and manufacture of contact lenses, it is an object of the present invention to provide improved organic silicate materials.
Another object of the invention is to provide an acrylic silicate having siloxane portions and one or more sites rendering it reactive so as to be polymerizable and/or able to be cross-linked with methyl methacrylate, methacrylic acid, and acrylic acid and cross-linking agents such as polyfunctional acrylic esters.
Another object of the invention is to provide a composition which includes a siloxanyl or silyloxy acrylic silicate which is resistant to hydrolytic decomposition.
Still another object of the invention is to provide an improved acrylic siloxanyl silicate able to be copolymerized with known materials for the manufacture of gas permeable contact lenses.
A further object is to provide a method of making polymerizable acrylic silicate materials.
Another object of the invention is to provide a contact lens made from a material which includes siloxanyl acrylic silicate portion and acrylic portion, and having one or more cross-linking and wetting agents forming a part thereof.
A still further object of the invention is to provide a contact lens made from polymers which are in turn comprised in part from such silicate monomers.
Another object of the invention is to provide one or mor acrylic silicate compositions wherein the acrylic portion is based on materials which make possible the production of a polymerizable silicate having methyl or ethyl acrylate comprising the acrylate portion as opposed to having the less reactive methyl methacrylate moiety forming such portions of the compositions.
Yet another object of the invention is to provide a reaction mechanism which permits the use of hydroxyethylmethacrylate (HEMA) or hydroxyethylacrylate (HEA) as a starting material rather than utilizing a methoxylated or ethoxylated methacryloxypropylsilane as a starting material in the production of a polymerizable monomer.
A further object of the invention is to provide one or more monomers wherein the polymerizable acrylic portion is based on HEMA or HEA, and wherein the silicon atom to which both the various siloxy or more complex groups of the acrylate portion are bonded to the acrylate containing portion by a carbon-oxygen-silicon linkage rather than the carbon silicon linkage characterizing prior art polymerizable acrylic silanes used for similar purposes.
Still another object is to provide a polymerizable silicate monomer having a terminal silicate group to which plural groups, such as sec-or-tert-butoxy groups, are used as substituents on silicon atoms which are bonded by an Si--O--Si linkage to the "terminal" silicon atom. The "terminal" atom as that term is used herein, means the silicon atom which forms a part of the C--O--Si linkage.
Another object is to provide a polymer of high oxygen permeability for non-optical uses, such as for use in analysis or treatment of blood or blood components, and for use in other medical or scientific apparatus.
The invention achieves these and other objects and advantages by providing acrylic silicates having the general formula: ##STR3## wherein R=alkyl, aryl or H,
R'=R or OR PA1 Y=alkyl, vinyl, aryl, or fluoroalkyl ##STR4## A=Y or H B=oxyalkyl, oxyaryl, oxyfluoroalkyl, oxyalkylacrylate, alkyl esters, aryl esters, fluoroalkyl esters, or acrylic esters.
The invention also achieves its objects by providing specific reactive silicate materials and methods of making them, as well as polymerized acrylic materials made from these starting materials.